1. Field of the Invention
The invention relates to an actuator control apparatus.
2. Description of the Related Art
There is a conventional electric power steering system that assists a driver's steering operation by applying driving force generated by a motor to a steering mechanism of a vehicle. A control apparatus of the electric power steering system acquires, for example, a steering torque, a vehicle speed and a value of electric current that is actually supplied to the motor, from various sensors. Then, the control apparatus computes a target current value based on the steering torque and the vehicle speed, and executes feedback control on the motor to make the actual current value coincide with the target current value.
Electric power steering systems are required to have high reliability, and therefore various measures against malfunctions of sensors are taken. For example, an electric power steering system described in Japanese Patent Application Publication No. 2000-185657 (JP 2000-185657 A) includes two torque sensors. Even if one of the two torque sensors of the electric power steering system malfunctions, application of steering assist force to a steering system is continued by utilizing sensor signals generated by the other one of the torque sensors, which is operating properly.
However, in the electric power steering system described in JP 2000-185657 A, the two torque sensors are individually connected to a control apparatus, and thus it is necessary to provide the control apparatus with a terminal used to connect the backup torque sensor to the control apparatus in addition to a terminal used to connect the main torque sensor to the control apparatus. Further, making other sensors redundant has been under consideration. Thus, the control apparatus needs to be provided with more terminals as the number of sensors increases. The same applies to control apparatuses that control actuators on the basis of information acquired from various electronic devices including sensors.